Concentric power connection for induction furnaces



June 9, 1959 F. KRALL ETAL 2,890,258

CQNCENTRIC POWER CONNECTION FOR INDUCTION FURNACES Fi led March 8. 1957 2 SheetsSheet 1 T I INVENTORS W, 4% ATTORNEYS June 9, 1959 F. KRALL ETAL CONCENTRIC POWER CONNECTION FOR INDUCTION FURNACES ,Filed March 8, 19 57 2 Shae ts-5heet 2 United States Patent ce Patented June 9, 1959 flexible insulating tubes to cool the electric wires extend- 2,890,258 ing therethrough.

I The means by which the object of the invention is obi gg gg yfi mgg FOR tained is described more fully with reference to the ac- Friedrich Kralt, Werner Scheibe, and Rolf Schuster,

Hanan (Main), Germany, assignors to Deutsche Goldund ilber-Scheideanstalt vormals Roessler, Frankfurt am Main, Germany Application March 8, 1957, Serial No. 644,839

Claims priority, application Germany March 9, 1956 3 Claims. (CI. 1331) This invention relates to the power supply for induc tion furnaces. In particular, the invention is directed to a flexible lead-in connection for the electric and cooling water supply for the furnace induction coil.

In high vacuum induction furnaces, the induction windings surrounding the melting pot are turnably mounted so as to permit the tilting of the pot. With Water cooled coils, the problem is to form a suitable turnable connection for the electric and Water supply lines. Heretofore, this has been accomplished by means of two concentric copper tubes which pass through the wall of the vacuum chamber; and on the outside, the electric lines are connected to the power supply by means of movable clamps or flexible cables.

However, these concentric constiuctional forms are characterized by their stiif and rigid construction. This causes the disadvantages principally in that the axis of the tilting axle of the pot must be exactly coaxial with the lead-in plug in the wall of the vacuum chamber. This requirement is not easily met, because the weight of the melting pot, together with the thermal strains in the" pot andvacuum chamber supports, can cause distortions of the tilting axle of the pot to appear under operating conditions, which causes jamming in the lead-in plug and faulty operation. Moreover, an exact alignment of the various heavy parts, such as the melting pot and the vacuum chamber, is very difiicult.

The object of the instant invention is to construct a flexible lead-in connection for the electric and Water lines attached to the induction coil of the melting pot in a vacuum chamber, so that the melting pot can be tilted and moved without disrupting the connection.

In general, the object is obtained by using tWo connecting joints, one mounted in the vacuum chamber wall and the other mounted in the chamber adjacent the induction coil. The inner joint adjacent the coil is a connection bearing composed of two concentric copper rings joined to the coil and turnable in a bearing mounting. In the wall of the vacuum chamber is a lead-in plug which supports the plug connection also composed of two concentric copper rings. These latter rings are connected to the power supply bus bars and are sealed to the wall of the chamber. Two concentric flexible insulating tubes, formed, for example, of polyvinylchloride, extend between the plug rings and the bearing rings. The tubes are tightly joined to the bearing rings; and, within the vacuum chamber, the opposite ends of the tubes are loosely fitted over the copper rings, but the outer tube is tightly fastened to the wall of the chamber. Flexible high frequency electric wires extend between the plug rings and bearing rings, respectively, with the ends of the wires permanently joined to the rings. In the upright vertical position of the melting pot, these wires are slack.

Provision is also made for passing cooling water through the rings. This cooling water not only flows through the tubular induction coil, but also through the companying drawings, in which:

Figure 1 is a longitudinal cross-sectional view through the flexible connection mounted in the wall of the vacuum chamber and attached to the induction coil for the melting pot;

Figure 2 is a cross-sectional view on the line 2-2 of Figure 1; and

Figure 3 is a cross-sectional view on the line 3-3 of Figure l.

The vacuum chamber 11 having wall 12 contains a melting pot 13, indicated by dashed lines, the pot being surrounded by the tubular induction coil 14 with the two ends 15 and 16. Pot 13 is turnable on an axle, indicated by its axis A. For reasons of clarity, the axle itself is not shown. This axle is supported by bearings 17 and 18. The axis B of the lead-in plug 19 is coaxial with axis A and extends through wall 12. Plug 19 is sealed in the wall by conventional packing held by the pressure rings 20. Plug 19 is composed of two concentric permanently mounted copper rings 21 and 22. These copper rings outwardly of wall 12 are joined to the power supply bus bars 23 and 24. Rings 21 and 22 also have openings for the water supply. Inlet water supply pipe 25 extends through ring 22, and the return water pipe 26 extends through ring 21.

The bearing connection is composed of concentric copper rings 27 and 28 mounted in bearing 17. Coil end 15 passes through ring 28, while end 16 passes through ring 27. Electric power for the coil must be led from ring 21 to ring 27 and from ring 22 to ring 28. This is accomplished by means of two circularly arranged groups of high frequency wires 29 and 30. These two groups of wires are respectively surrounded by polyvinylchloride insulating tubes. The outer wire 29 is surrounded by tube 31, while the inner wire 30 is surrounded by tube 32. In the connection bearing, tubes 31 and 32 are tightly fastened to rings 27 and 28, with the tube 31 surrounding the outer periphery of ring 27 and the tube 32 surrounding ring 28 and forming an insulating seal between rings 27 and 28. Tube 32 also provides insulation between wires 29 and 30. In the plug 19, mounted in Wall 12, tubes 31 and 32 are loosely fitted over rings 21 and 22. The inner tube 32 provides the insulation between rings 21 and 22. The outer ring is tightly fitted against the packing held by the pressure rings 20.

The cooling water flows through pipe 25 into the space 33, within tube 32, and then through coil end 15 into the coil and out through coil end 16 into space 34 Within tube 31, and then drains through pipe 26. Consequently, Wires 29 and 30 mounted in spaces 33 and 34 are washed and cooled by the Water.

Wires 29 and 30, as well as tubes 31 and 32, are flexible and elastic. Therefore, any misalignment of the axes A and B Will not cause a jamming thereof. Optimumably, axes A and B are in coaxial alignment.

The copper rings 27 and 28, together With the tubes 31 and 32, constitute a unique body which is turnable within bearing 17 and which is joined to ends 15 and 16 of coil 14. This connection bearing is turned when the pot, together with its coil, is tilted. Tubes 31 and 32 are slidable in plug 19 so that they can move around independently of the fixed rings 21 and 22. The ends of wires 29 and 30 are fixed to the respective copper rings with the ends of the wires fastened to rings 27 and 28, being movable therewith. This permits a turning of the wires through an angle as great as Fig. 2 reflects cross-sectional view 2--2 and Fig. 3

cross-sectional view -3--3'in Fig. 1. In both cases 29 and 30 represent the two groups of high frequency wires, and 31 and 32 the polyvinyl chloride insulating tubes. As in Fig. 1 the pressure rings are marked 24), the water supply pipe 2 and thereturnwatenpipe 26. In Fig. 3, 15 and 16 represent the ends of the induction coil and simultaneously the water supply-pipeandthe return water pipe for the induction coil. 'Ballbearing 17 shown in Fig. 'l is here divided in the fixed part 17a, the movable part 1712, and the balls 170.

As wires 29 and 30 as well as tubes 31 and 32 are flexible 'and elastic, an axis 'misalignments expected to occur in practice, and also a restricted longitudinal movement of "tubes 31 and 32 is possible without entailing leakage of the pressure rings 20. Tubes 31 and 32 are fitted over rings 21 and 22 so as to, on'the one hand, allow rotation within the fixed rings, and on the other hand, avoid 'thatpractically no cooling water contained in space 33 flows'frorn space 33 into space 34.

Having now described the means by 'which'the object of the invention 'is obtained,we claim:

1. An electric power and water line connection for high vacuum induction furnaces having a melting pot with an induction coil contained within the wall of a vacuum chamber comprising a connection bearing within said chamber between said wall and pot and coaxial with the tilting axis of said pot composed of inner and outer concentric copper bearing rings, means mounting said ringsfor rotation around said axis, and means electrically connecting said rings, respectively, to said induction coil; a connection plug mounted in thewall of said chamber'composed of inner and outer concentric copper plug rings respectively coaxial With said bearing rings electrically joined to bus bars outside of said chamber; an inner and an outer polyvinylchloride flexible insulating tube, an end of the inner tube spacing said inner and outer bearing rings, 'and an end of said outer tube enclosing said outer bearing ring, with the opposite end of said inner tube loosely fitted between said inner and outer plug rings, and the opposite end of the outer tube loosely covering the outer plug ring but tightly fitted to the outer circumference of said plug; and flexible wire electrical conductors extending between the outer rings, and the inner rings, respectively, said conductors being slack when said melting pot is in vertical position.

2. An electric power and'water line connection as in claim 1, further comprising coolingwater inlet and outlet pipe lines connected, respectively, with said inner and outer plug rings for providing cooling water to the spaces within said insulating tubes and to said induction coil.

3. An electric power and water line connection for high vacuum induction furnaces having a melting pot with an induction coil contained Within the wall of a vacuum chamber-comprising a connection bearing within said chamber between said wall and potcomposed of inner and outer concentric copperbearing rings, means mounting said rings for rotation about their axis, and means electrically connecting said rings, respectively, to said induction coil; a connection plugmounted' in the wall of said-chamber composed of inner and outer concentric copper plug rings, respectively, electrically joined to bus bars outside ofsaid chamber; an inner and an outer polyvinylchloride fiexible insulating tube, an end of the inner tube spacing said inner and outer bearing rings, and an end of said outer tube enclosing said outer bearing ring, with the opposite end of said inner tube loosely fitted between said innerand outer plug rings, and the opposite end-of the outer tube loosely covering the outer plug ring but tightly fitted-to the outer circumference 'ofsaid plug; and flexible wire electrical conductors extending between the outer rings, and the inner rings, respectively, said conductors being slack when said melting pot is in vertical position. 

